3GPP Long Term Evolution, LTE, is the fourth-generation mobile communication technologies standard developed within the 3rd Generation Partnership Project, 3GPP, to improve the Universal Mobile Telecommunication System, UMTS, standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs. The Universal Terrestrial Radio Access Network, UTRAN, is the radio access network of a UMTS and Evolved UTRAN, E-UTRAN, is the radio access network of an LTE system. In an UTRAN and an E-UTRAN, a user equipment, UE, also known as a wireless device, is wirelessly connected to at least one radio access node, commonly referred to as a NodeB, NB, in UMTS, and as an evolved NodeB, eNodeB or eNode B, in LTE. A radio access node is a general term for a radio network node capable of scheduling transmission to and from wireless device and transmitting radio signals to a UE and receiving signals transmitted from a UE.
In 3GPP systems, a wireless device is allowed to attach to and access a wireless communication network if the wireless device is associated with a subscription that allows the wireless communication network to authenticate the wireless device.
Today wireless devices, such as mobile phones, typically support other wireless technologies such as Wireless Local Area Networks, commonly referred to as WLAN, in addition to the cellular standards. As a means to improve the network capacity in future networks, WLAN is intended to be an integral part. That is, WLAN will be regarded as just another radio access technology, so that handover can be made to WLAN or from WLAN without the user noticing that the service is no longer being carried by 3GPP technologies like WCDMA or LTE.
Mobile operators are today mainly using WLAN to offload traffic from the mobile networks but the opportunity to improve end user experience regarding performance is also becoming more important. The current WLAN deployments are basically totally separate from mobile networks, and are to be seen as non-integrated. The usage of WLAN is driven due to the free and wide unlicensed spectrum, and the increased availability of WLAN in mobile terminals like smart phones and tablets. The end users are also becoming more and more at ease with using WLAN for example at offices and homes.
Portable wireless devices today usually support both WLAN/Wi-Fi and a number of 3GPP cellular technologies, but many of the terminals are basically behaving as two separate devices, from a radio access perspective. The 3GPP radio access network and the modems and protocols that are operating pursuant to the 3GPP specifications are basically unaware of the wireless access Wi-Fi protocols and modems that are operating pursuant to the Wi-Fi 802.11 specifications, as defined by both IEEE and Wi-Fi Alliance. UE is the 3GPP term for the portable wireless device while the term STA is used in Wi-Fi. In the following disclosure, the term wireless device will be used to mean a device operating pursuant to any 3GPP specification or similar specification, as well as pursuant to a WLAN specification, e.g. the 802.11 specifications.
As pointed above, up until now 3GPP and Wi-Fi have evolved as two separate systems, being standardized up to a great extent in isolation. However, recent activities in 3GPP and Wi-Fi Alliance, WFA, have taken the initiative to improve the interoperability of the two systems and provide mobile operators with a greater control over their “operator-deployed” WLANs.
Presently handover to or access selection of the WLAN radio access network is controlled by the wireless device, rather than by the network, due to that the WLAN network is still not sufficiently tightly integrated with the cellular networks using 3GPP technologies. However, using WLAN is from a user perspective often preferred, because of the lower cost associated with it. Therefore, an access selection of WLAN is often performed as soon as a WLAN network is detected and the signal strength is sufficiently high. Hence, when wireless device is in range of a WLAN network it will typically connect to this wireless network when the received signal strength indication, RSSI, is sufficiently high, without further analysis.
A further level of integration can be realized via access selection based on radio access network information on both 3GPP and Wi-Fi, in addition to the common authentication and user plane integration methods.
In order to achieve this functionality it is required to link or connect the wireless device context in the 3GPP RAN, which holds information about radio performance, UE mobility etc. on the 3GPP side, with the UE context in the WLAN network. This can then enable a network entity to take decisions whether the wireless device should access the WLAN network or not depending on if the wireless device is stationary, and/or has a good connection to the WLAN AP etc. The decision can then be signaled to the wireless device or executed internally in the 3GPP/WLAN network, e.g. to control admission of the wireless device to WLAN.
Known methods to support handover from “3GPP” to WLAN has the property that a relatively long time may elapse between the network commanding the wireless device to perform handover to Wi-Fi, and when the wireless device finally starts using the Wi-Fi for user plane transmission. The reason for this is lengthy procedures performed on the Wi-Fi side after the network command to move to Wi-Fi. This behavior doesn't really provide good network control as the wireless device behavior is not really predictable. Also, the situation for the wireless device may have changed once it actually starts using the Wi-Fi access.